Drive mechanism for automatic dissolves in motion picture cameras



July 10, 1962 E c. MANDERFELD 3,043,185

DRIVE MECHANISM FOR AUTOMATIC DISSOLVES IN MOTION PICTURE CAMERAS Filed Jan. 18, 1960 M fli/IAMUEL aMMDEQFELQ INVENTDR.

United States Patent 3,043,185 DRIVE MECHANISM FOR AUTOMATIC DIS- SOLVES IN MOTION PICTURE CAMERAS Emanuel. .C. Manderfeld, Hollywood, Calif., assignor to Mitchell Camera Corporation, Glendale, Califi, a corporation of Delaware Filed Jan. 13, 1960, Ser. No. 3,162 2 Claims. (CI. 88-16) In motion picture cameras employing an automatic dissolve shutter, the dissolve is power operated from the camera driving motor. Such driving motors are usually of the three phase type, and frequently when a motor is in-' stalled its electrical feed may be mistakenly connected to cause motor rotation in the direction opposite to that which properly operates the dissolve. And that results in jamming, or frequently in gear stripping, when the dissolve mechanism comes up against its limiting stops. The purpose of the present invention is to obviate the possibility of any such damage.

How this is accomplished is explained in the following descriptions, with reference to a standard type of dissolve mechanism shown in the accompanying drawings, in which:

FIG. 1 is a section showing in simplified form the elements of a typical dissolve shutter;

FIG. 2 is a schematic perspective showing the dissolve drive with the present invention; and

FIGS. 3 and 4 are schematic sections on line 33 of FIG. 2.

Referring first to FIG. 1, a two-blade dissolve shutter is shown at 12, with blade 10 mounted on interior shaft 14 and blade 12 on the exterior hollow shaft 16. The shutter as a whole is driven through suitable gearing such as that indicated at 18; and rotational movement of shafts 14 and 16 relative to each other shifts the apertured shutter blades relative to each other to cause the shutter opening to close down or open up, in the manner well known in the art.

To cause that relative movement, the two shafts are interconnected by a spiral splining. As shown here a member such as 20 is slidably splined at 22 on shaft 14 and is externally spirally splined as at 24 in an end portion 17 of external shaft 16. Member 20 rotates with the whole shutter shaft, but its longitudinal movement, as by longitudinal shifting of such a rotatably stationary member 26, shifts the rotational relationship between shafts 14 and 16 and between the shutter blades. In the schematic showing of FIG. 2 the longitudinally shiftable member 26 is schematically indicated at 26a; the external shutter shaft at 16, and the shutter drive gearing at 18, 19. Driving gear 19 is fixed on shaft 30 which is driven, mediately or immediately, by motor 32. During camera operation, shaft 30 is constantly driven.

As here shown, the shutter dissolve drive train involves a gear 34 on drive shaft 30, driving a gear 36 which carries, or its shaft carries, a spur gear 38 with which a pinion 40 meshes. Another pinion 42, immediately above 40, meshes with that pinion but not with 38; so that the two pinions are rotated in opposite directions.

Both pinions 40 and 42 are axially slidable and are normally held in positions to the left in FIGS. 2, 3 and 4 by springs such as indicated at 44 in FIG. 2. They may individually be manually pushed to the right in those figures, as by the buttons indicated at 45. In their positions to the right they engage teeth 46 of rack 48; in their positions to the left theydisengage the rack. Gear 38, and the two pinions, are long enough that pinion 40 engages 38, and pinion 42 engages 40, in either longitudinal position of either pinion. FIG. 3 shows the lower pinion 40 to the right, engaging rack teeth 46; FIG. 4 shows the upper pinion 42 to the right engaging the rack teeth.

3,043,185 Patented July 10, 1962 ice Meshing engagement of one or the other of the pinions with the rack drives the latter up or down. Vertical movement of the rack drives the shifting member 26a (26 in FIG. 1) axially through the medium of a spiral gear sector 50 connected to 48 by the link 52 and meshing with a spiral rack 54 on 26a. The numeral 60 generally designates an indicator driven from rack 48 to visually show the degrees of shutter opening.

Assume the normal direction of rotation of driving shaft 30 to be as indicated by the arrows and that of gear 36 to be as indicated. The normal directions of rotation of pinions 48 and 42 are then as indicated by the arrows. Shifting the rotating pinion 40 into mesh with rack 48 will then move the rack up. When the shutter mechanisms have reached the limit of their movements in one direction, the rack recess 56 comes opposite 40 and movement of the rack and its connected shutter parts stop. In such position the shutter opening is either fully open or fully closed. In that position of the parts pinion 40 is no longer operative to move the rack and shift the shutter opening. But pinion 42 is then in position to mesh with the rack teeth, and when meshed will move the rack down and shift the shutter opening oppositely to its shift by pinion 40. When the shutter mechanisms have reached their limiting positions in that direction, recess 58 comes opposite pinion 42 and the movement of the rack and the shutter mechanism stops.

The dissolve drive mechanism usually has physical stops limiting relative shutter blade movements in the opposite directions. Those stops may be on the shutter blades themselves and they may be so located here; but they are here shown as stops 60 on the rack that bring up against the fixed rack guides 62 as the shutter blades reach their limiting relative positions and recesses 56 and 58 come into register with pinions 4i) and 42.

Driving gear 34 for the dissolve drive is normally fixed on driving shaft 30. If, then, driving motor 32 is connected up to rotate shaft 30 in the direction opposite to that indicated, pinions 40 and 42 will be constantly driven in directions opposite to those indicated. Pinion 40 when meshed with the rack will then drive the rack down. The physical movement stop, here illustrated as the lower stop 60, will then bring up against its stop shoulder 62 with recess 58 opposite pinion 42, not pinion 40. Unless pinion 44) is released before that occurs the drive mechanism will be jammed and the teeth of one or more of the driving gears (commonly of Bakelite or other plastic) stripped off. The same things will occur if pinion 42 is meshed with the rack, driving the rack up and bringing upper stop 60 up against its stop shoulder 62 before recess 56 can reach that pinion.

All those difliculties are here entirely obviated by providing a one-Way or over-run drive between drive shaft 30 and driving gear 34 to drive that gear only in the normal, indicated, direction. As here shown, gear 19 carries a cylindrical hub fixed to that gear. A spiral spring 72 closely surrounds hub 70 and has one end 74 attached to gear 34. The other end of the spring bears against gear 19 which is fixed on drive shaft 30. The coiling of spring 72, here shown as left-handed, is such that rotation of 19 and hub 70 in the normal, proper, direction contracts the spring around hub 78 to positively drive gear 34. On the other hand, if shaft 30 and gear 19 are rotating in the opposite and wrong direction, the drag of 20 on the spring expands it if there is any resistance to the rotation of gear 34. Consequently the driving torque on gear 34 in that direction is small or negligible and when the movement of the shutter dissolve drive mechanism is stopped, no damaging force is exerted on any of its parts.

I claim:

1. In a shutter dissolve mechanism for a camera, a multiple bladed apertured shutter in which relative movement between the shutter blades varies the size of the shutter aperture, a motor driven driving shaft adapted to be rotated in a forward or a reverse direction, a driving train for relatively moving the shutter blades, said driving train including a gear toothed member movable in opposite directions and connected to the shutter blades to correspondingly move tthem relatively in opposite directions, a pair of gears driven in opposite directions from the dn'ving shaft, said gears being each independently movable into and out of mesh with the gear toothed member, movement stops associated with the driving train and limiting the movements of the gear toothed member and the shutter blades in opposite directions, and the driving connection between the driving shaft and the pair of oppositely driven gears including an over-running drive element that forcibly drives said pair of gears when the driving shaft is rotating only in said forward direction.

2. In a shutter dissolve mechanism for a camera, a multiple bladed ap'ertured shutter in which relative movement between the shutter blades varies the size of the shutter aperture, a motor driven driving shaft adapted to be driven in a forward or a reverse direction, a driving train for relatively moving the shutter blades, said driving train including a gear toothed rack movable in opposite directions and connected to the shutter blades to correspondingly move them relatively in opposite directions, a pair of oppositely rotating gears each independently movable into and out of mesh with the rack, a gear train driving said pair of gears from the driving shaft and including a driving gear driven from said driving shaft, movement stops associated with the driving train and limiting the movements of the rack and the shutter blades in opposite directions and a normally engaged over-running drive element in said gear train that forcibly drives said driving gear from said driving shaft when that shaft is rotating only in said forward direction and disengages when that shaft is rotating in said reverse direction.

References Cited in the file of this patent UNITED STATES PATENTS 328,126 Long Oct. 13, 1885 1,417,005 Wescott May 23, 1922 1,629,420 Starkey May 17, 1927 2,088,715 Mitchell Aug. 3, 1937 2,341,389 Whittaker Feb. 15, 1944 

